This invention relates to sealing arrangements for electronic circuit modules, and particularly but not exclusively to sealing arrangements for electronic circuit modules for use in automotive applications.
In the automotive industry, electronic circuits are used in many applications within vehicles. For example, electronic circuits are now used in the field of engine management control, where a microprocessor is programmed to receive inputs from sensors and then provides instructions to various transducers for optimising variable engine parameters.
In such an application, and referring to FIG. 1, there is shown a module 5, which is often located in close proximity to the engine (not shown). Electronic circuitry 10 of the module 5 is typically housed in a casing 20, to protect delicate components of the circuitry 10 from oil, grease, water and extremes of temperature.
A problem with this arrangement is that the casing should be watertight, but in order to prevent an air pressure differential from building up the casing should also be air-permeable.
It is known to provide a breather device, such as a dedicated vent 25 as shown in FIG. 2. A typical vent may comprise a hole 30 formed in the casing 20 with a carrier piece 40 disposed in the hole 30 and containing an air-permeable membrane 50. An o-ring seal 70 is provided to seal the space between the carrier piece 40 and the casing 20. An intricate covering piece 60 overlies the membrane (in order to protect against clogging of the membrane by oil and grease) but at the same time has a network of small channels 65 which facilitate movement of air through the covering piece 60, so as to provide the vent.
However the manufacture of the above vent 25, including the provision of a breather hole 30 in the casing 20, the carrier piece 40 for the membrane which is disposed in the hole (with the seal 70), the complex protective covering piece 60 (with the channels 65) which must be secured to the encapsulating piece, adds further expense, time and complexity to the overall manufacture of the module 20.
This invention seeks to provide a sealing arrangement for an electronic circuit module which mitigates the above mentioned disadvantages.
According to a first aspect of the present invention there is provided a sealing arrangement for an electronic circuit module as claimed in claim 1.
In this way a seal is provided using an air-permeable, water-impermeable membrane in a simple and inexpensive arrangement, which protects the membrane from damage.